Defoliate further or stop?

Hey gardener, I admit I'm having a hard time understanding this new trend. Back in my day, we did the opposite; we kept the leaves and waited for them to fall off on their own. I've read some things about defoliation, and from what I've read, you need to remove all the leaves that block light from the lower branches. So if I go by that, you can still remove some leaves. Bella ciao!